(CNN) -- "I am like, I am so (BLEEP) high. This is terrible. And I did it in that voice. And I have never done that voice before in my life. I don't know where that voice came from. But I heard myself use that voice. And in my mind, I went, oh (BLEEP). I just gave myself Down syndrome." --Wyatt Cenac, This American Life, 5/4/2014

It's hard to build a more inclusive society when people keep making fun of you. Even as people with disabilities and their allies make progress in so many ways, disability remains a target for mockery.

David M. Perry

Over the last few days, a baby boy with Down syndrome named Gammy has been all over the news. He and his twin sister were born to a surrogate mother in Thailand, but allegedly when their Australian parents discovered the boy's genetic condition, they left him behind.

To the biological parents, it seems, the words "Down syndrome" meant that he was not worth being their son.

These are the stakes involved in how we talk and think about disability, how we portray disability in the media, not to mention in our schools and homes.

I'm the father of a boy with Down syndrome. I remember weeping when I heard the diagnosis. My mother said she couldn't stop thinking about how he'd be taunted and bullied as he got older. Her experience of people with intellectual disabilities was that they were targets for cruel humor.

The good news is that in recent years, sustained awareness campaigns against dehumanizing speech, coupled with some 20 years of inclusive education since the passage of the Americans With Disabilities Act in 1990, have made things a lot better in America. No one is likely to call my son the r-word to his face.

The bad news is that perhaps we have focused too much on explicit language without addressing the deeper questions of portrayal and representation. Too often, people with disabilities are marginalized and excluded. Instead of focusing on a single word, we've got to work to unravel the prejudices beneath the surface.

Last May, Wyatt Cenac, former "Daily Show" correspondent and comedian, appeared on "This American Life," a popular show on National Public Radio. He told a story about a bad experience eating a pot brownie. The joke was that it made him talk, uncontrollably, in a funny voice, as if he had Down syndrome.

Next, Cenac, broke the flow of the piece in order to issue a kind of disclaimer. He said:

"Now let me just say, I know what Down syndrome is. I know that Down syndrome is something that you're born with when you are born with an extra chromosome. I know all that information. I knew that information then. But something about eating this brownie made me think that somehow I had grown an extra chromosome and I now had adult-onset Down syndrome. And for people who have Down syndrome, it's something they grow up with. And they grow up and they have healthy and happy lives. I just got it."

Then he went right back to his fake voice, slurring words, and sounding confused.

"I agree with you completely that nobody should have to listen to stories that mock and denigrate (people with Down syndrome) This was a concern for me and my producers when we were working with Wyatt Cenac. We talked about it as we shaped the story."

He then notes that Cenac went out of his way to make the disclaimer, claims that Cenac is making himself the butt of the joke, and that, "The only thing that possibly could be offensive is his imitation of what a person with Down syndrome sounds like, and again -- we may disagree about that -- I think that's fair game for a comedian."

Glass and Cenac used the disclaimer, used the statement that they know what Down syndrome is, medically, as a way to protect themselves from criticism. However, as Glass admits, the humor of this piece depends on making fun of the way that some people with Down syndrome speak.

Since my son was very young, we've worked for so many hours on his speech. Together, we've worked with many therapists to carve out individual phonemes, tones, sounds and finally words. Each tiny advance takes months. I wept when I heard him say, "I love you" for the first time, even though it was in a slurred, indistinct voice of the exact type that Cenac was mocking. Moreover, speech is so fraught, because intelligibility -- how clearly my son can communicate with strangers -- determines what kind of independence will be possible for him as an adult.

There is no disclaimer that can take the sting out of Cenac's joke. He and Glass can decide that the humor of the piece is worth being offensive, but they don't get to determine whether the hurt is real or just. Neither do the many comics that rely on punching down, using mockery of people marginalized by ability, race, religion, gender or sexuality to get a laugh.

Cenac isn't alone. Ricky Gervais, in the British TV show "Derek," plays a man who appears to be disabled. Derek is supposed to be a positive example, but much of the comedy extends from his disabled physicality -- a hunched back, a slacked toothsome mouth, and a shuffling walk. Other laughs come from his cluelessness as he cheerily staggers through uncomfortable scenes.

Gervais has said he doesn't mean to make fun of people with intellectual disabilities, saying in an interview, "I've never considered him disabled; he is a 'out of the mouth of babies' innocent person who always says the right thing that you didn't see coming. And if I say he's not disabled, that's the end of it."

That's not the end of it. Not for Gervais. Not for Cenac.

In the end, it doesn't matter whether a comedian uses a diagnostic term, issues a disclaimer, or claims to be the butt of the joke. Humor can reinforce stereotypes or destroy them. When you make fun of attributes associated with disability, you might as well just be standing on stage, shouting the r-word.